1. Field of the Invention
The present invention relates to an igniting operation that ignites fuel during running of an internal combustion engine, and relates to an ignition controlling apparatus that determines whether this igniting operation is being implemented normally.
2. Description of the Related Art
In recent years, problems of environmental protection and fuel depletion have been raised, and responding thereto has also become a major task in the automotive industry. In response thereto, many techniques have been developed that attempt to raise internal combustion engine efficiency to a maximum. One of these is a stratified charge combustion control method in which flow is controlled such that fuel is distributed only in a vicinity of a spark ignition source (a spark plug), and combustion is generated using a quantity of fuel that is significantly reduced relative to volume of air that is charged inside an internal combustion engine combustion chamber.
A difficulty with stratified charge combustion control is stabilizing the concentration of the fuel in the vicinity of the spark plug. At present, this is difficult to stabilize, and in order to implement stratified charge combustion using existing techniques, it is necessary to adopt either a long electrical discharge method, in which spark discharge is continued until fuel in the vicinity of the spark plug reaches a combustible air-fuel ratio, or a multiple ignition method, in which sparks are repeatedly generated many times.
The above long electrical discharge method is a method in which the ignition coil becomes large and heavy, and there is a practical limit at a discharge time of approximately 2 msec. In contrast, a small, light ignition coil that has superior responsiveness is used in the multiple ignition method, and although single discharge time is short, by generating this repeatedly it is possible to lengthen the discharging zone significantly, and in recent years a tendency to adopt the multiple ignition method has become more pronounced.
However, in the case of multiple ignition systems, each discharging period is often set so as to be short, at approximately 100 to 200 μsec, and if conditions arise in which large capacity components combine on the ignition instruction pathway, ignition interrupting instructions may not be transmitted to the ignition coil as expected, and as a result multiple ignition may not be achieved, leading to deterioration in exhaust gases (emissions) that accompanies deterioration in combustibility, deterioration in fuel consumption that accompanies decline in output, etc., thereby giving rise to problems with regard to environmental protection.
Other techniques for raising engine efficiency include configurations that increase an engine compression/expansion ratio to a limit. A problem with these techniques is that internal portions of the combustion chamber reach extremely high temperatures during the compression cycle and the fuel ignites spontaneously. Combustion due to such spontaneous ignition is extremely fast, and it has been found experimentally that in most cases combustion is completed before the ignition instruction or during the spark discharge immediately after instruction.
As a means of detecting such spontaneous ignition, systems have been proposed that determine spontaneous ignition generating conditions from a state of ions that are formed together with combustion, but since this ion detection is not possible during spark discharge, detection of such spontaneous ignition combustion is enabled by applying multiple ignition to terminate the spark discharge forcibly. Here too, because it becomes impossible to detect spontaneous ignition if ignition interrupting instructions are not transmitted to the ignition coil as expected, as described above, it is consequently impossible to increase the compression ratio of the engine, leading to deterioration in fuel consumption, etc., due to deterioration in thermal efficiency, and compounding the problems with regard to environmental protection.
If intermittent interference from the power supply system wiring is generated in the ignition instruction supply line, then ignition due to passage and interruption of electric current to the ignition coil may be repeated at a timing that is different than the intended ignition timing regardless of the ignition instruction, and in such cases, there is also a possibility that this may lead to damage to the engine.
Consequently, it is necessary to diagnose whether ignition is being performed as intended.
[Patent Literature 1]
Japanese Patent No. 3488405 (Gazette)
The apparatus that is shown in the above patent literature diagnoses operation of an ignition coil by detecting an impulse signal that is generated together with operation of the ignition coil, and can determine when the ignition coil is not operating at all. However, it cannot determine whether or not the multiple ignition that has been described above has been implemented. Since the impulse signal that accompanies ignition is generated if the last spark is implemented even if multiple ignition has not been achieved, the apparatus that is shown in the patent literature is limited to determination of normal ignition, and cannot determine when multiple ignition is abnormal.
There are also cases in which the apparatus that is shown in the patent literature cannot correctly determine when the ignition coil is operating in an unintended manner. When the spark plug is in a clean state, even the apparatus that is shown in the patent literature can determine abnormal ignition if the igniting operation has not been performed within a set detection period. However, if a conducting pathway has formed between a center electrode and ground of the spark plug due to carbon, etc., there are cases in which leakage current flows during the detection period even if the igniting operation has not been implemented within the detection period, and another problem has been that the apparatus that is shown in the patent literature mistakes this leakage current for the signal that accompanies the igniting operation and cannot determine that the igniting operation is abnormal.